The frequency range between 1 GHz and 30 GHz is called the microwave range (MW range). The frequency range from 30 GHz upward is called the millimeter wave range (mmw range). Extremely high frequency modules differ from high frequency modules in particular in the fact that for extremely high frequency circuits at 5 GHz and higher as a rule “waveguides,” e.g., microstrip lines and coplanar lines, are used.
Extremely high frequency modules are electronic components which fulfill a variety of functionalities for applications intended for use in the frequency range from 1 to 100 GHz. Such components may be employed in general in data transmission systems, e.g., for satellite television reception, for wireless local data networks—LANs (local area networks), WLANs (wireless LANs), Bluetooth, optical modules such as multiplexers, modulators and transceiver units—as well as for radar and for front-end modules for broadband communication, e.g., LMDS (local multimedia distribution systems) and directional radio equipment for base stations.
Most modules that operate in the millimeter wave range are produced today on the basis of thin film substrates containing integrated circuits. The thin film substrate can carry one or more chip components at the same time. The chip components are attached to the carrier substrate by means of wire bonding or the flip-chip technique and are connected to it electronically. The contact paths between the chip components and the substrate are kept as short as possible, so that the signal losses, which come to light in particular when a component containing open signal—carrying lines is encapsulated with a casting compound, may be minimized.
Because of relatively high costs, the chip area of the semiconductor chip components is kept very small, which results in correspondingly small dimensions of the external contacts of such components. The contact size of a microwave IC is usually around 50 to 100 μm; the interval between the external contacts varies between 100 and 250 μm. For technological reasons, the minimum spacing between two inter-layer connections in the substrate for example is 225 μm. In principle it is possible to bring the interval of the external contacts of a microwave IC to the minimum interval between the inter-layer connections. This involves an unwanted enlargement of the chip area, however. Another problem is that for technological reasons it is not possible to apply conductor lines of any desired fineness in the substrate or on the top surface of the substrate.